Forge welding, also called fire welding, is a solid-state welding process that joins two pieces of metal by heating them to a high temperature and then hammering them together. It may also consist of
Sponge iron traditionally used to forge the Japanese blade nihonto.
Pattern welding is a smithing practice of folding and/or twisting metal, possibly multiple pieces that are forge-welded. This results in differing layers in a pattern, hence the name. This process was
A contemporary pattern-welded sword blade made by Danish swordsmith Ejvind Nørgård. The blade shows a chevron pattern with opposing twists and straight laminate alternating.
An image of a modern pattern welded knife blade, showing the dramatic patterning on the side below, and the layering of the steel in the spine above. Acid etching darkens the 1080 plain carbon steel more than it does the 15N20 low alloy nickel steel, producing alternating bands of light and dark on the surface.